Transceiver interface having staggered cleave positions

ABSTRACT

The disclosure generally relates to sets of optical waveguides such as optical fiber ribbons, and fiber optic connectors useful for connecting multiple optical fibers such as in optical fiber ribbon cables. In particular, the disclosure provides an efficient, compact, and reliable optical fiber connector that incorporates an optically transmissive substrate combining the features of optical fiber alignment, along with redirecting and shaping of the optical beam.

TECHNICAL FIELD

The present invention relates to an optical connector for connectingsets of optical waveguides such as optical fiber ribbons.

BACKGROUND

Optical fiber connectors are used to connect optical fibers in a varietyof applications including: the telecommunications network, local areanetworks, data center links, and for internal links in high performancecomputers. These connectors can be grouped into single fiber andmultiple fiber designs and also grouped by the type of contact. Commoncontact methods include: physical contact wherein the mating fiber tipsare polished to a smooth finish and pressed together; index matched,wherein a compliant material with an index of refraction that is matchedto the core of the fiber fills a small gap between the mated fibers'tips; and air gap connectors, wherein the light passes through a smallair gap between the two fiber tips. With each of these contact methods asmall bit of dust tips of the mated fibers can greatly increase thelight loss.

Another type of optical connector is referred to as an expanded beamconnector. This type of connector allows the light beam in the sourceconnector to exit the fiber core and diverge within the connector for ashort distance before the light is collimated to form a beam with adiameter substantially greater than the core. In the receiving connectorthe beam is then focused back to its original diameter on the tip of thereceiving fiber. This type of connector is less sensitive to dust andother forms of contamination.

The optical cables used in many applications make use of fiber ribbons.These ribbons are comprised of a set of coated fibers joined together ina line (typically 4, 8 or 12 fibers in a line). The individual glassfibers with their protective coatings are typically 250 microns indiameter and the ribbons typically have a fiber to fiber pitch of 250microns. This 250 micron spacing has also been used in opticaltransceivers with a variety of designs spacing the active opticaldevices at the same 250 micron spacing.

Currently available expanded beam multiple fiber connectors typicallylimit the beam diameter to 250 microns to match the ribbon pitch. Inorder to achieve a beam diameter greater than the fiber pitch, currentconnectors require the fiber ribbon to be manually split into singlefibers before mounting the fibers on the connector.

In general, single fiber optical connectors include a precisioncylindrical ferrule for aligning and contacting optical fiber end faceswith each other. The optical fiber is secured in the central bore of theferrule so that the fiber's optical core is centered on the ferruleaxis. The fiber tip is then polished to allow physical contact of thefiber core. Two such ferrules can then be aligned with each other usingan alignment sleeve with the polished fiber tips pressed against eachother to achieve a physical contact optical connection from one fiber toanother. Physical contact optical connectors are widely used.

Multiple fiber connectors often use a multiple fiber ferrule such as theMT ferrule to provide optical coupling from the source fibers to thereceive fibers. The MT ferrule guides the fibers in an array of moldedbores to which the fibers are typically bonded. Each ferrule has twoadditional bores in which guide pins are located to align the ferrulesto each other and thus align the mated fibers.

A variety of other methods have also been used to make fiber to fiberconnections. Included are V-groove alignment systems such as found inVolition™ optical fiber cable connectors, and bare fiber alignment in anarray of precise bores. Some connecting concepts such as described in,for example, U.S. Pat. Nos. 4,078,852; 4,421,383, and 7,033,084 make useof lenses and/or reflecting surfaces in optical fiber connections. Eachof these connecting concepts describes single purpose connectionsystems, such as an in line connector or a right angle connector.

It would be advantageous to provide an expanded beam connector that canterminate fiber ribbons without separating the fibers and also provide abeam with a diameter greater than the fiber-to-fiber pitch.

SUMMARY

The disclosure generally relates to sets of optical waveguides such asoptical fiber ribbons, and fiber optic connectors useful for connectingmultiple optical fibers such as in optical fiber ribbon cables. Inparticular, the disclosure provides an efficient, compact, and reliableoptical waveguide connector that incorporates a optically transmissivesubstrate combining the features of optical waveguide alignment, alongwith redirecting and shaping of the optical beam.

In one aspect, the present disclosure provides an optical constructionthat includes: an optically transmissive substrate having: a first majorsurface including a plurality of waveguide alignment features; anopposing second major surface including a plurality of microlensesstaggered relative to one another; and a plurality of optical waveguideswith angle cleaved end faces disposed adjacent the first major surface.The angle cleaved end faces are staggered relative to one another, eachangle cleaved end face of an optical waveguide in the plurality ofoptical waveguides corresponding to a different microlens and beingoriented so that light exiting each optical waveguide is directed by theangle cleaved end face to the corresponding microlens through thesubstrate. In another aspect, the present disclosure also provides anoptical connector including the optical construction. In still anotheraspect, the present disclosure also provides a transceiver including theoptical construction.

In another aspect, the present disclosure provides an opticalconstruction that includes: a first major surface having a firstplurality of waveguide alignment features; a first plurality of opticalwaveguides with angle cleaved end faces disposed adjacent the firstmajor surface, the angle cleaved end faces being staggered relative toone another; a second major surface opposite the first major surface andcomprising a second plurality of waveguide alignment features; and asecond plurality of optical waveguides with angle cleaved end facesdisposed in adjacent the second major surface, the angle cleaved endfaces being staggered relative to one another. Each optical waveguide inthe first plurality of optical waveguides corresponds to a differentoptical waveguide in the second plurality of optical waveguides, theangle cleaved faces of corresponding optical waveguides being sooriented that light exiting one optical waveguide enters thecorresponding optical waveguide. In another aspect, the presentdisclosure also provides an optical connector including the opticalconstruction. In still another aspect, the present disclosure alsoprovides a transceiver including the optical construction.

In yet another aspect, the present disclosure provides an opticalconstruction that includes: an optically transmissive substrate having afirst major side including a first floor surface; a first staircaseformed on the first floor surface and including at least a first stepcomprising a first tread; a second major side opposite the first majorside and having a second floor surface; a second staircase formed on thesecond floor surface and including at least a first step having a firsttread. The optically transmissive substrate further includes a firstplurality of staggered microlenses disposed on the second floor surfaceand forming rows of microlenses; a second plurality of staggeredmicrolenses disposed on the first tread of the second staircase andforming rows of microlenses, wherein the substrate, the first and secondstaircases and the microlenses form a unitary construction. The opticalconstruction further includes a first plurality of optical waveguideswith angle cleaved end faces disposed on the first floor surface, theangle cleaved end faces being staggered relative to one another; and asecond plurality of optical waveguides with angle cleaved end facesdisposed on the first tread of the first staircase, the angle cleavedend faces being staggered relative to one another, wherein each anglecleaved end face of an optical waveguide in the first and the secondplurality of optical waveguides corresponds to a different microlens sothat light exiting each optical waveguide is directed by the anglecleaved end face to the corresponding microlens through the substrate.In another aspect, the present disclosure also provides an opticalconnector including the optical construction. In still another aspect,the present disclosure also provides a transceiver including the opticalconstruction.

The above summary is not intended to describe each disclosed embodimentor every implementation of the present disclosure. The figures and thedetailed description below more particularly exemplify illustrativeembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the specification reference is made to the appended drawings,where like reference numerals designate like elements, and wherein:

FIG. 1A shows a cut-away perspective view of a fiber optic connector;

FIG. 1B shows a cut-away perspective view of a fiber optic connector;

FIG. 1C shows a perspective view of a fiber optic connector;

FIG. 2A shows a top perspective schematic view of an opticallytransmissive substrate;

FIG. 2B shows a bottom perspective schematic view of an opticallytransmissive substrate;

FIG. 3A shows a top perspective schematic view of an opticallytransmissive substrate;

FIG. 3B shows a bottom perspective schematic view of an opticallytransmissive substrate;

FIG. 4 shows a cross-sectional schematic view of an optical connection;

FIGS. 5A-5C show schematic views of optical fiber and microlenspositioning; and

FIG. 6 shows a cross-sectional schematic view of an optical connection.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

This application is related to U.S. Pat. No. 9,207,413, which isincorporated by reference.

The present disclosure relates sets of optical waveguides such asoptical fiber ribbons, and fiber optic connectors useful for connectingmultiple optical fibers such as in optical fiber ribbon cables. Thedescription that follows is directed toward connections of opticalfibers and optical fiber ribbon cables; however, it is to be understoodthat the present disclosure is similarly directed to connections ofoptical waveguides including, for example, planar optical waveguidesthat can be fabricated from polymeric materials or glasses.

There are a number of optical fiber connector features that users ofoptical fibers desire, which are not found in currently availableproducts. These features include low cost, robust performance againstcontamination, easy cleaning, compact designs, and the ability torapidly and repeatedly connect multiple optical fibers with a singleconnector. A rapidly growing application for high capacityinterconnections is between equipment racks in data centers where datarates of 10 Gb/s are common, and link lengths are relatively short(typically a few to 100 meters). In such applications, multiple singlefiber connectors are often ganged together. Accordingly, describedherein is a multiple fiber connecting technique and article which cansignificantly reduce the cost of multi-fiber connecting.

In both single fiber and multi-fiber device interfaces it is oftendesirable to maintain a low profile interface. This is oftenaccomplished by routing the fiber parallel to the circuit board andusing a reflective surface to turn the light so that the beam isperpendicular to the board at the chip interface. It is also common tomake use of small lenses to improve the coupling efficiency between thedevice and the fiber. In the case of ribbon fiber interfaces, theselenses have a center to center distance of 250 um to match with thespacing in the ribbon. Often an MT ferrule is also included as part ofthe transceiver package with the ferrule's alignment pins being used toalign the fibers to the lenses.

In one particular embodiment, the present disclosure provides a generalpurpose connecting element for multi-fiber optical connectors thatinclude an optically transmissive substrate that makes use of angledreflecting surfaces and a microlens array to redirect and focus orcollimate the optical beams. The redirected beams emerge from theelement perpendicular to a planar mating surface. The microlens elementscan be located in a pocket and can be slightly recessed from the matingsurface. The connecting elements also include mechanical features tofacilitate alignment of the microlens arrays of the two mated parts. Inone particular embodiment, the reflecting surfaces may be cleaved endsurfaces that can be aligned at an angle to the optical axis of theoptical fiber. In some cases, the reflective surface may be coated witha reflecting material such as a metal or metal alloy to redirect thelight. In some cases, the reflective surface may instead enable TotalInternal Reflection (TIR) to facilitate redirecting the light.

The optically transmissive substrate can be encased in a connectorhousing that can provide support for the optical cable, ensure alignmentof interlocking components of the connector element, and provideprotection from the environment. Such connector housings are well knownin the art, and can include, for example, alignment holes, matchingalignment pins, and the like. The same connecting element can be used ina variety of connecting configurations. It can also be used to interfaceoptical fibers to optical devices such as VCSELs and photodetectorsusing a board mounted alignment ring. It is to be understood thatalthough the disclosure provided herein describes light travelling inone direction through the fiber and the connector, one of skill in theart should realize that light could also travel in the oppositedirection through the connector, or could be bi-directional.

The relatively simple design used for both the optically transmissivesubstrate and the connector housing, eliminates the use of fine corepins such as in an MT ferrule molding, and as a result, the cost andcomplexity of the molded, cast, or machined part is reduced.Furthermore, a general purpose connecting element described herein canbe used in a variety of applications, thereby allowing both developmentcosts and manufacturing costs to be spread across higher volume,decreasing the cost per part. Still further, the use of an expandedoptical beam from focusing or collimating microlenses can also providefor improved resistance to transmission losses due to dirt or otherimpurities.

In one particular embodiment, the unique interface defined herein can beused for making internal links within high performance computers,servers, or routers. Additional applications in mating to optical backplanes can also be envisioned. Some of the prominent features of theconnecting elements can include: a molded (or cast, or machined)component having a generally planar mating surface, and a recessed area(pocket) within the mating surface; convex microlens features located onthe floor of the pocket with the apex of these microlens features beingwithin the pocket volume so that when two elements are mated with theirmating surfaces in contact, a small gap exists between the microlensfeatures; optical fiber alignment features useful to align the opticalfibers axes generally within about 15 degrees of parallel to the matingsurface; and reflecting surfaces to redirect the optical beam from eachfiber so that they are perpendicular to the mating surface. Each opticalbeam is centered over one of the microlens features; and mechanicalalignment features facilitate the alignment of two connecting elementsso that their mating surfaces are in contact and their microlenses arealigned.

In one particular embodiment, the microlens features may collimate thelight beam from the fiber. Generally, collimated light can be useful formaking fiber-to-fiber connections, since the light beam is generallyexpanded upon collimation, which makes the connection less susceptibleto contamination by foreign material such as dust. In one particularembodiment, the microlens features may instead focus the beam so as tocreate a beam “waist” in the plane of the mating surface. Generally,focused beams can be useful for making fiber-to-circuit connections suchas to a sensor or other active device disposed on a circuit board, sincethe light beam can be concentrated to a smaller region for greatersensitivity. In some cases, particularly for optical fiber-to-fiberconnections, collimation of the light beam may be preferred, since thecollimated light beams are more robust against dirt and othercontamination, and also provide for greater alignment tolerances.

In one particular embodiment, the optical fibers can be aligned usingwaveguide alignment features, such as within molded vee-groove featuresin the optically transmissive substrate, with the vee-grooves beingparallel to the mating surface; however, vee-grooves are not requiredfor alignment in all cases. As described herein, optional parallelvee-grooves are included, but it is to be understood that othertechniques for alignment and securing of the optical fibers would alsobe acceptable. Furthermore, vee-grooved alignment may not be suitable insome cases and other techniques may be preferred, for example, when theoptical waveguide is a planar optical waveguide. In some cases, thealignment of the optical waveguides and/or optical fibers can instead beaccomplished by any of the techniques known to one of skill in the artof optical alignment using any suitable waveguide alignment feature.

A variety of mechanical feature sets may be used to align a pair ofconnecting elements. One feature set includes a pair of preciselypositioned holes into which alignment pins are placed, similar to thealignment technique used for MT ferrules. In one particular embodiment,if the holes diameters and locations are similar to that of the MTconnector, then one of the connecting elements described herein could(with an appropriate set of microlenses) intermate with an MT ferrule.

Coupling the light from optical fiber to optical fiber, fromsemiconductor light sources to optical fibers, and the related couplinglight from optical fibers to photodetector chips, has been done in awide variety of ways. Achieving the desired low loss and low cost hasbeen challenging. This is especially so when the fibers are grouped intoindustry standard ribbons. These ribbons contain a number of coatedfibers (typical numbers are 8 or 12) having an outside diameter of about250 um. The fibers are then laminated between a pair of thin polymerfilms to make a flat ribbon. Another technique for fabricating ribbonsis to use an extrusion process wherein the individual coated fibers areguided through an extrusion die with a polymeric matrix material.

The present disclosure provides an improvement on previous multifiberinterfaces, including transceiver interfaces, by providing a fiberribbon that includes individual fibers cleaved at more than one lengthto allow greater space between optical devices reducing electricalinterference and also allowing the use of lenses having a largerdiameter to allow more effective optical coupling. In one particularembodiment, the individual fibers can be cleaved at more than one lengththat results in a staggered pattern of the cleaved ends. The staggeredpattern can include several rows of fiber ends, each row includingfibers cleaved at the same length, whereas adjacent rows includeadjacent fibers that are cleaved at a different length.

The present disclosure relates in part to optical transceiver interfacesused in communication and computer networks for both external andinternal links. The transceivers may be located on a motherboard,daughter board, blade, or may be integrated into the ends of an activeoptical cable.

With the ever increasing data rates, it becomes increasingly difficultto package sensitive photodetectors close to the higher powersemiconductor lasers without electromagnetic interference problems.Furthermore, as bit rates increase the beam divergence of verticalcavity surface emitting lasers (VCSELs) increases. These issues make itdesirable to increase the device spacing and the lens diameter.

In some cases, to minimize Fresnel loss, it can be desirable to haveonly a single air gap between the devices and the fiber cores. Toachieve this, the present disclosure provides that the fibers can beadhesively attached to the optically transmissive substrate along theirbottom side with an index matching adhesive.

Given this configuration and the numerical aperture of the fiber, a 500um lens allows the lens block to be manufactured without extremely finesections which would be difficult to mold. Cleave patterns other thanthe two rows shown here are also possible and would enable even largerlens diameter and device spacing.

FIG. 1A shows a cut-away perspective view of a fiber optic connector 100according to one aspect of the disclosure. Fiber optic connector 100includes a connector housing 110 having an optional cover support 115,an optional cover (not shown) that fits within the optional coversupport 115 to protect the optical components of the fiber opticconnector 100 from the environment, and an alignment feature 150. Anoptically transmissive substrate 120 having a plurality of optionalparallel vee-grooves 126 for accepting individual optical fibers 132from an optical ribbon cable 130 is secured within connector housing110. The individual optical fibers 132 each include a cleaved end 136disposed in a staggered orientation forming at least a first opticalfiber row 135 a and a second optical fiber row 135 b. It is to beunderstood that any desired number of optical fiber rows can staggeredrelative to each other, as described elsewhere. In operation, each ofthe cleaved ends 136 associated with each of the individual opticalfibers 132 re-direct light through optically transmissive substrate 120and out through a microlens 128 disposed on lower surface 122. Themicrolenses 128 can be disposed in a cavity 140 such that the lenssurface is indented from the bottom of the connector housing 110. Thecleaved ends 136 can be laser cleaved optical fibers that forms anoblique angle with the axis of the fiber, as described elsewhere. Insome cases, the cleaved optical fibers can be coated with a reflectorsuch as a metal or metal alloy. In some cases, the cleaved opticalfibers can instead re-direct light by total internal reflection (TIR).

Optically transmissive substrate 120 can be fabricated from any suitablytransparent and dimensionally stable material including, for example,polymers such as a polyimide. In one particular embodiment, opticallytransmissive substrate 120 can be fabricated from a dimensionally stabletransparent polyimide material such as, for example, Ultem 1010Polyetherimide, available from SABIC Innovative Plastics, PittsfieldMass. In some cases, the individual optical fibers 132 can be adhesivelysecured in the optional parallel vee-grooves 126. In one particularembodiment, an index matching gel or adhesive may be inserted betweenthe optically transmissive substrate 120 and the individual opticalfibers 132. By eliminating any air gap in this area, Fresnel losses maybe greatly reduced.

FIG. 1B shows a cut-away perspective view of a fiber optic connector 101attached to a circuit board 170. The housing components shown in FIG. 1Ahave been removed in FIG. 1B to more clearly show the relationship ofthe optical ribbon cable 130, the individual optical fibers 132, thecleaved ends 136, and the optional vee-grooves of the opticallytransmissive substrate 120. As described elsewhere, each of the firstrow 135 a and second row 135 b of cleaved ends 136 of optical fibers 132are associated with a first row and a second row of microlenses (notshown). The microlenses (and thus the cleaved ends 136) can be alignedby alignment features 150 and alignment ring 160, to any desired opticaldevice (not shown, but located under optically transmissive substrate120) positioned on circuit board 170.

FIG. 1C shows a perspective view of the fiber optic connector 100 ofFIG. 1A connected to a second fiber optic connector 100′. Second fiberoptic connector 100′ can be identical to the fiber optic connector 100,and forms an optical connection 102, as described elsewhere. Optionalcover 117 is disposed optional cover support 115 (shown in FIG. 1A) toprotect the optical components of the fiber optic connector 100 from theenvironment. Alignment features 150 serve to ensure that light fromoptical ribbon cable 130 and second optical ribbon cable 130′ arecoupled efficiently, with a minimum of losses.

FIG. 2A shows a top perspective schematic view of an opticallytransmissive substrate 220, according to one aspect of the disclosure.Optically transmissive substrate 220 includes a first surface 224 havinga plurality of optional parallel vee-grooves 226, and an opposing secondsurface 222. A plurality of input optical fibers (two are shown as firstinput optical fiber 232 a and a second input optical fiber 232 b) arepositioned along optional parallel vee-grooves 226, and may be adheredto the optional parallel vee-groove 226, as described elsewhere. Each ofthe input optical fibers 232 a, 232 b, are cleaved at an oblique angleto the axis of the input optical fibers 232 a, 232 b, forming a firstcleaved end 236 a and a second cleaved end 236 b within a first cleavedend row 235 a, such that injected light is re-directed into theoptically transmissive substrate 220. In some cases, the light can bere-directed at an angle perpendicular to the axis of the input opticalfibers 232 a, 232 b.

FIG. 2B shows a bottom perspective schematic view of the opticallytransmissive substrate 220 of FIG. 2A. Optically transmissive substrate220 includes the first surface 224 and the opposing second surface 222having a plurality of microlenses 228 a, 228 b, 228 c, 228 d, that aredisposed within a microlens pocket 240. Each of the plurality ofmicrolenses 228 a, 228 b, 228 c, 228 d are aligned with a cleaved end236 a, 236 b, in first cleaved end row 235 a described above, and aredisposed to receive re-directed light from the respective optical fiber232 a, 232 b. Each of the microlenses have a microlens diameter D1, andare disposed within microlens pocket 240 with a center-to-center spacingL1. The center-to-center spacing L1 typically is no greater than thespacing between adjacent optical fibers, and results in a restriction onthe maximum microlens diameter D1 that can be utilized in the connector,as described elsewhere. The depth of microlens pocket 240 serves to keepeach of the microlenses below the level of opposing second surface 222.It is to be understood that optically transmissive substrate 220 caninclude any desired number of optional parallel vee-grooves 226, cleavedends 236 a-236 b, rows of cleaved ends 235 a, microlenses 228 a-228 d,and input optical fibers 232 a, 232 b.

FIG. 3A shows a top perspective schematic view of an opticallytransmissive substrate 320, according to one aspect of the disclosure.Optically transmissive substrate 320 includes a first surface 324 havinga plurality of optional parallel vee-grooves 326 that are aligned with aplurality of light re-directing features 335 a, 335 b, 335 c, 335 d, andan opposing second surface 322. A plurality of input optical fibers (twoare shown as first input optical fiber 332 a and a second input opticalfiber 332 b) are positioned along optional parallel vee-grooves 326, andmay be adhered to the optional parallel vee-groove 326, as describedelsewhere. Each of the input optical fibers 332 a, 332 b, are cleaved atan oblique angle to the axis of the input optical fibers 332 a, 332 b,forming a first cleaved end 336 a within a first cleaved end row 335 a,and a second cleaved end 336 b within a second cleaved end row 335 b,such that injected light is re-directed into the optically transmissivesubstrate 320. In some cases, the light can be re-directed at an angleperpendicular to the axis of the input optical fibers 332 a, 332 b.

FIG. 3B shows a bottom perspective schematic view of the opticallytransmissive substrate 320 of FIG. 3A. Optically transmissive substrate320 includes the first surface 324 and the opposing second surface 322having a plurality of staggered microlenses 328 a, 328 b, 328 c, 328 d,that are disposed within a microlens pocket 340. Each of the pluralityof staggered microlenses 328 a, 328 b, 328 c, 328 d are aligned with acleaved end 336 a, 336 b in a first and second row 335 a, 335 b,described above, and is disposed to receive light from the respectiveoptical fibers 332 a, 332 b. Each of the staggered microlenses 328 a,328 b, 328 c, 328 d have a staggered microlens diameter D2, and aredisposed within microlens pocket 340 with a center-to-center spacing L1corresponding to the separation of the optical fibers, and thecenter-to-center spacing L1 of adjacent microlenses 328 a-328 d can bethe same as the center-to-center spacing L1 described with reference toFIG. 2B. However, each of the staggered microlenses 328 a, 328 b, 328 c,328 d have a staggered spacing L2 corresponding to the separation of themicrolenses, and the staggered spacing L2 is larger than thecenter-to-center spacing L1. As a result, the maximum microlens diameterD2 that can be utilized in the connector is greater for the staggeredspacing L2 shown in FIG. 3B, as compared to the maximum microlensdiameter D1 that can be utilized in the microlens spacing L1, asdescribed elsewhere.

As a result of staggering the cleaved ends 336 a, 336 b, the pluralityof staggered microlenses 328 a, 328 b, 328 c, 328 d, enable an increasein the microlens diameter D1 to the staggered microlens diameter D2. Alarger staggered microlens diameter D2 is preferred. The depth ofmicrolens pocket 340 serves to keep each of the microlenses below thelevel of opposing second surface 322. It is to be understood thatoptically transmissive substrate 320 can include any desired number ofoptional parallel vee-grooves 326, cleaved ends 336 a-336 b, rows ofcleaved ends 335 a, 335 b, microlenses 328 a-328 d, number of rows ofmicrolenses 328 a-328 d, number of microlenses 328 a-328 d in each row,and input optical fibers 332 a, 332 b.

In contrast with the embodiment shown in FIGS. 2A-2B, the microlenslocations shown in FIG. 3B are not defined as a single row. In this casetwo rows of microlenses are shown with two microlenses in each row. Whenused with optical fiber ribbons having a 250 micron fiber-to-fiberspacing, this allows the microlenses to approach 500 microns indiameter. The use of 500 micron diameter collimating microlensespossible with the staggered fiber/microlens embodiment shown in FIGS.3A-3B, allows an alignment tolerance that is less stringent than isrequired with 250 micron diameter microlenses possible with theembodiment shown in FIGS. 2A-2B, and much less stringent than needed forphysical contact connectors using conventional MT ferrules. It is to beunderstood that any of the optical connectors described herein caninclude staggered cleaved ends and correspondingly staggered microlensesas described with reference to FIGS. 3A-3B, and it may be preferable toinclude the staggered configurations wherever possible. Generally, thedescribed staggered microlens designs can enable an expanded-beamoptical fiber connector that can be used for a ribbonized collection offibers, wherein the optical beam diameter exiting the microlenses isgreater than the fiber-to-fiber separation (that is, pitch) in theribbon, and the fibers do not need to be singulated in order toaccomplish the connection.

FIG. 4 shows a cross-sectional schematic view of an optical connection401 that includes a first optical connector 400 connected to a secondoptical connector 400′, according to one aspect of the disclosure. InFIG. 4, the cross-sectional view is near the optical axis (that is,center) of a pair of optical fibers in communication through theconnector. In one particular embodiment, second optical connector 400′can be identical to the first optical connector 400, and forms theoptical connection 401, similar to the optical connection 101 shown inFIG. 1B.

First optical connector 400 includes a first connector housing 410 and afirst optically transmissive substrate 420 secured within the firstconnector housing 410. The first optically transmissive substrate 420includes a first upper surface 424 and an opposite first lower surface422. A first optical fiber 432 is secured within a first optionalparallel vee-groove 426 on first upper surface 424, between the firstoptically transmissive substrate 420 and the first connector housing410. The first connector housing 410 further includes an optional firstcover support 415, and an optional first cover 417 that can serve toprotect the components in the first optical connector 400.

First optical fiber 432 includes a first light re-directing feature 435including a first cleaved end 436 of first optical fiber 432. Firstoptical fiber 432 can be held in position and aligned by resting in thefirst optional parallel vee-groove 426, which can be directly moldedinto first optically transmissive substrate 420. First optical fiber 432can be in direct contact with first upper surface 424 such that firstgap 434 is eliminated. In some cases, an adhesive can be used to affixthe first optical fiber 432 to the first optional parallel vee-groove426 and an index-matching adhesive or gel can fill the first gap 434, ifpresent.

First optically transmissive substrate 420 further includes a firstmicrolens 428 disposed on the first lower surface 422, positioned suchthat a central light ray 490 travelling through the first optical fiber432 that intercepts and is reflected from the first cleaved end 436, isdirected toward the optical center of the first microlens 428. In oneparticular embodiment, shown in FIG. 4, first cleaved end 436 can bedisposed such that central light ray 490 intercepts first cleaved end436 at a reflection angle θr equal to about 45 degrees. In some cases,first cleaved end 436 can be a TIR surface. In some cases, first cleavedend 436 can instead be a mirrored reflective surface.

In a similar manner, second optical connector 400′ includes a secondconnector housing 410′ and a second optically transmissive substrate420′ secured within the second connector housing 410′. The secondoptically transmissive substrate 420′ includes a second upper surface424′ and an opposite second lower surface 422′. A second optical fiber432′ is secured within a second optional parallel vee-groove 426′ onsecond upper surface 424′, between the second optically transmissivesubstrate 420′ and the second connector housing 410′. The secondconnector housing 410′ further includes an optional second cover support415′, and an optional second cover 417′ that can serve to protect thecomponents in the second optical connector 400′.

Second optical fiber 432′ includes a second light re-directing feature435′ including a second cleaved end 436′ of second optical fiber 432′.Second optical fiber 432′ can be held in position and aligned by restingin the second optional parallel vee-groove 426′, which can be directlymolded into second optically transmissive substrate 420′. Second opticalfiber 432′ can be in direct contact with second upper surface 424′ suchthat second gap 434′ is eliminated. In some cases, an adhesive can beused to affix the second optical fiber 432′ to the second optionalparallel vee-groove 426′ and an index-matching adhesive or gel can fillthe second gap 434′, if present.

Second optically transmissive substrate 420′ further includes a secondmicrolens 428′ disposed on the second lower surface 422′, positionedsuch that a central light ray 490 travelling through the second opticalfiber 432′ that intercepts and is reflected from the second cleaved end436′, is directed toward the optical center of the second microlens428′. In one particular embodiment, shown in FIG. 4, second cleaved end436′ can be disposed such that central light ray 490 intercepts secondcleaved end 436′ at a reflection angle θr equal to about 45 degrees. Insome cases, second cleaved end 436′ can be a TIR surface. In some cases,second cleaved end 436′ can instead be a mirrored reflective surface.

A first and a second alignment feature 450, 450′ in first and secondconnector housing 410, 410′, respectively, serve to ensure that lightfrom the first optical fiber 432 and the second optical fiber 432′ arecoupled efficiently, with a minimum of losses. First and secondalignment features 450, 450′ can include any suitable feature to ensurealignment of the first and second optical connectors 400, 400′, and thefeatures shown in FIG. 4 are for illustrative purposes only.

A first optical fiber separation distance S1 can be measured between theoptical axis of the first optical fiber 432 and the first microlens 428.A second optical fiber separation distance S1′ can be measured betweenthe optical axis of the second optical fiber 423′ and the secondmicrolens 428′. A microlens separation distance S2 can be measuredbetween the surfaces of the first and second microlenses 428, 428′. Insome cases, each of the first optical fiber separation distance S1 andthe second optical fiber separation distance S1′ will be the same, andcan range from about 1 mm to about 2 mm, or about 1.5 mm. The microlensseparation distance S2 can range from about 0.1 mm to about 1 mm, orabout 0.5 mm.

A light beam 490 travelling through first optical fiber 432 is reflectedfrom first cleaved end 436 in a direction perpendicular to the opticalaxis of first optical fiber 432. Light beam 490 then passes throughfirst microlens 428 which can be a collimating microlens or a focusingmicrolens, as described elsewhere. Light beam 490 then enters secondoptically transmissive substrate 420′ through second microlens 428′, isreflected from second cleaved end 436′ and enters second optical fiber432′ in a direction parallel to the optical axis of the second opticalfiber 432′.

FIGS. 5A-5C show schematic views of optical fiber and microlenspositioning, according to one aspect of the disclosure. In FIG. 5A, eachof the optical fibers 532 in ribbon cable 530 have an uncoated fiberdiameter fl equal to about 125 microns, and a fiber-to-fiber spacing dlequal to about 125 microns. In one particular embodiment, for two rowsof microlenses 528 shown in the figure, the staggered cleaved ends 536of optical fibers 532 can be separated by a fiber length difference L1equal to about 433 microns, and the maximum diameter D1 of themicrolenses 528 can be about 500 microns.

In FIG. 5B, each of the optical fibers 532 in ribbon cable 530′ have anuncoated fiber diameter fl equal to about 125 microns, and afiber-to-fiber spacing dl equal to about 125 microns. In one particularembodiment, for three rows of microlenses 528 shown in the figure, thestaggered cleaved ends 536 of optical fibers 532 can be separated by afiber length difference L2 equal to about 707 microns, and the maximumdiameter D2 of the microlenses 528 can be about 750 microns.

In FIG. 5C, each of the optical fibers 532 in ribbon cable 530″ have anuncoated fiber diameter fl equal to about 125 microns, and afiber-to-fiber spacing dl equal to about 125 microns. In one particularembodiment, for four rows of microlenses 528 shown in the figure, thestaggered cleaved ends 536 of optical fibers 532 can be separated by afiber length difference L3 equal to about 968 microns, and the maximumdiameter D3 of the microlenses 528 can be about 1000 microns.

FIG. 6 shows a cross-sectional schematic view of an optical connection601 that includes a first optical connector 600 connected to a secondoptical connector 600′, according to one aspect of the disclosure. InFIG. 6, the cross-sectional view is near the optical axis (that is,center) of two pairs of optical fibers in communication through theconnector. In one particular embodiment, second optical connector 600′can be identical to the first optical connector 600, and forms anoptical connection 601, similar to the optical connection 101 shown inFIG. 1B. In some cases, second optical connector 600′ can instead be amirror image to the first optical connector 600.

First optical connector 600 includes a first connector housing 610 and afirst optically transmissive substrate 620 secured within the firstconnector housing 610. The first optically transmissive substrate 620comprises a staircase that includes a first floor surface 624, a firststep 625, and a first tread 627. The first optically transmissivesubstrate 620 further comprises a second floor surface 622 opposite thefirst floor surface 624 and a second tread 621 opposite the first tread627. A first optical fiber 632 is secured within a first optionalparallel vee-groove 626 on first floor surface 624, between the firstoptically transmissive substrate 620 and the first connector housing610. A second optical fiber 631 is secured within a second optionalparallel vee-groove 629 on the first tread 627, and is also securedwithin first connector housing 610. The first connector housing 610further includes an optional first cover support 615, and an optionalfirst cover 617 that can serve to protect the components in the firstoptical connector 600.

First optical fiber 632 includes a first light re-directing feature 635including a first cleaved end 636 of first optical fiber 632. Firstoptical fiber 632 can be held in position and aligned by resting in thefirst optional parallel vee-groove 626, which can be directly moldedinto first optically transmissive substrate 620. First optical fiber 632can be in direct contact with first floor surface 624 such that firstgap 634 is eliminated. In some cases, an adhesive can be used to affixthe first optical fiber 632 to the first optional parallel vee-groove626 and an index-matching adhesive or gel can fill the first gap 634, ifpresent.

Second optical fiber 631 includes a second light re-directing feature637 including a second cleaved end 638 of second optical fiber 631.Second optical fiber 631 can be held in position and aligned by restingin the second optional parallel vee-groove 629, which can be directlymolded into first optically transmissive substrate 620. Second opticalfiber 631 can be in direct contact with first tread 627 such that secondgap 639 is eliminated. In some cases, an adhesive can be used to affixthe second optical fiber 631 to the second optional parallel vee-groove629 and an index-matching adhesive or gel can fill the second gap 639,if present.

First optically transmissive substrate 620 further includes a firstmicrolens 628 disposed on the second floor surface 622, positioned suchthat a light ray travelling through the first optical fiber 632 thatintercepts and is reflected from the first cleaved end 636, is directedtoward the optical center of the first microlens 628. First opticallytransmissive substrate 620 still further includes a second microlens 623disposed on the second tread 621, positioned such that a light raytravelling through the second optical fiber 631 that intercepts and isreflected from the second cleaved end 638, is directed toward theoptical center of the second microlens 623.

In a similar manner, second optical connector 600′ includes a secondconnector housing 610′ and a second optically transmissive substrate620′ secured within the second connector housing 610′. The secondoptically transmissive substrate 620′ comprises a staircase thatincludes a third floor surface 624′, a second step 625′, and a thirdtread 627′. The second optically transmissive substrate 620′ furthercomprises a fourth floor surface 622′ opposite the third floor surface624′ and a fourth tread 621′ opposite the third tread 627′. A thirdoptical fiber 632′ is secured within a third optional parallelvee-groove 626′ on third floor surface 624′, between the secondoptically transmissive substrate 620′ and the second connector housing610′. A fourth optical fiber 631′ is secured within a fourth optionalparallel vee-groove 629′ on the third tread 627′, and is also securedwithin second connector housing 610′. The second connector housing 610′further includes an optional second cover support 615′, and an optionalsecond cover 617′ that can serve to protect the components in the secondoptical connector 600′.

Third optical fiber 632′ includes a third light re-directing feature635′ including a third cleaved end 636′ of third optical fiber 632′.Third optical fiber 632′ can be held in position and aligned by restingin the third optional parallel vee-groove 626′, which can be directlymolded into second optically transmissive substrate 620′. Third opticalfiber 632′ can be in direct contact with third floor surface 624′ suchthat third gap 634′ is eliminated. In some cases, an adhesive can beused to affix the third optical fiber 632′ to the third optionalparallel vee-groove 626′ and an index-matching adhesive or gel can fillthe third gap 634′, if present.

Fourth optical fiber 631′ includes a fourth light re-directing feature637′ including a fourth cleaved end 638′ of fourth optical fiber 631′.Fourth optical fiber 631′ can be held in position and aligned by restingin the fourth optional parallel vee-groove 629′, which can be directlymolded into second optically transmissive substrate 620′. Fourth opticalfiber 631′ can be in direct contact with third tread 627′ such thatfourth gap 639′ is eliminated. In some cases, an adhesive can be used toaffix the fourth optical fiber 631′ to the fourth optional parallelvee-groove 629′ and an index-matching adhesive or gel can fill thefourth gap 639′, if present.

Second optically transmissive substrate 620′ further includes a thirdmicrolens 628′ disposed on the fourth floor surface 622′, positionedsuch that a light ray travelling through the third optical fiber 632′that intercepts and is reflected from the third cleaved end 636′, isdirected toward the optical center of the third microlens 628′. Secondoptically transmissive substrate 620′ still further includes a fourthmicrolens 623′ disposed on the fourth tread 621′, positioned such that alight ray travelling through the fourth optical fiber 631′ thatintercepts and is reflected from the fourth cleaved end 638′, isdirected toward the optical center of the fourth microlens 623′.

A first and a second alignment feature 650, 650′ in first and secondconnector housing 610, 610′, respectively, serve to ensure that lightfrom the first optical fiber 632 and the fourth optical fiber 431′ arecoupled efficiently, and also that light from the second optical fiber631 and the third optical fiber 632′ are coupled efficiently, with aminimum of losses. First and second alignment features 650, 650′ caninclude any suitable feature to ensure alignment of the first and secondoptical connectors 600, 600′, and the features shown in FIG. 6 are forillustrative purposes only.

A first optical fiber separation distance S1 can be measured between theoptical axis of the first optical fiber 632 and the first microlens 628.A second optical fiber separation distance S1′ can be measured betweenthe optical axis of the fourth optical fiber 631′ and the fourthmicrolens 623′. A first microlens separation distance S2 can be measuredbetween the surfaces of the first and fourth microlenses 628, 623′.Similarly, a third optical fiber separation distance S3 can be measuredbetween the optical axis of the second optical fiber 631 and the secondmicrolens 623. A fourth optical fiber separation distance S3′ can bemeasured between the optical axis of the third optical fiber 632′ andthe third microlens 628′. A second microlens separation distance S4 canbe measured between the surfaces of the second and third microlenses623, 628′.

In some cases, each of the first through fourth optical fiber separationdistances S1, S1′, S3, S3′, can be the same, and can range from about 1mm to about 2 mm, or about 1.5 mm. In some cases, each of the first andsecond microlens separation distance S2, S4, can be the same, and canrange from about 0.1 mm to about 1 mm, or about 0.5 mm. In oneparticular embodiment, each of the connection path lengths through theconnector can be the same, such that the first-fourth optical fiber pathlength S1+S2+S1′ is equal to the second-third optical fiber path lengthS3+S4+S3′.

A first light beam 690 travelling through first optical fiber 632 isreflected from first cleaved end 636 in a direction perpendicular to theoptical axis of first optical fiber 632. First light beam 690 thenpasses through first microlens 628 which can be a collimating microlensor a focusing microlens, as described elsewhere. First light beam 690then enters second optically transmissive substrate 620′ through fourthmicrolens 623′, is reflected from fourth cleaved end 638′ and entersfourth optical fiber 631′ in a direction parallel to the optical axis ofthe fourth optical fiber 631′.

In a similar manner, a second light beam 691 travelling through secondoptical fiber 631 is reflected from second cleaved end 638 in adirection perpendicular to the optical axis of second optical fiber 631.Second light beam 691 then passes through second microlens 623 which canbe a collimating microlens or a focusing microlens, as describedelsewhere. Second light beam 691 then enters second opticallytransmissive substrate 620′ through third microlens 628′, is reflectedfrom third cleaved end 636′ and enters third optical fiber 632′ in adirection parallel to the optical axis of the third optical fiber 632′.

In one particular embodiment, an antireflective (AR) coating can beapplied to portions of the optically transmissive substrate, the opticalfiber, or to both the optically transmissive substrate and the opticalfiber, in order to further reduce reflective (that is, Fresnel) losses.In some cases, an AR coating can be applied in the region proximate eachof the gaps between the optical fiber and the optically transmissivesubstrate (for example, the first through fourth gaps 634, 639, 634′,639′). In some cases, an AR coating can also be applied to the surfaceof the microlenses. In one particular embodiment, an index matching gelor an index matching adhesive can be disposed in the region surroundingthe gaps between the optically transmissive substrate and the opticalfiber, also to reduce reflective losses.

Following are a list of embodiments of the present disclosure.

Item 1 is an optical construction comprising: an optically transmissivesubstrate comprising: a first major surface comprising a plurality ofwaveguide alignment features; an opposing second major surfacecomprising a plurality of microlenses staggered relative to one another;and a plurality of optical waveguides with angle cleaved end facesdisposed adjacent the first major surface, the angle cleaved end facesbeing staggered relative to one another, each angle cleaved end face ofan optical waveguide in the plurality of optical waveguidescorresponding to a different microlens and being oriented so that lightexiting each optical waveguide is directed by the angle cleaved end faceto the corresponding microlens through the substrate.

Item 2 is the optical construction of item 1, wherein the waveguidealignment features comprise parallel grooves.

Item 3 is the optical construction of item 1 or item 2, wherein theoptical waveguides comprise optical fibers.

Item 4 is the optical construction of item 1 to item 3, wherein thestaggered microlenses form spaced apart first and second rows ofmicrolenses and the staggered angle cleaved end faces form spaced apartfirst and second rows of angle cleaved end faces.

Item 5 is the optical construction of item 1 to item 4, wherein each ofthe angle cleaved end faces comprise a total internal reflection (TIR)surface.

Item 6 is the optical construction of item 1 to item 5, wherein each ofthe angle cleaved end faces comprise a reflective material coating.

Item 7 is the optical construction of item 6, wherein the reflectivematerial coating comprises a metal or a metal alloy.

Item 8 is the optical construction of item 1 to item 7, wherein eachmicrolens includes a diameter greater than a separation distance betweenadjacent optical waveguides.

Item 9 is the optical construction of item 1 to item 8, furthercomprising an antireflective coating disposed on each microlens.

Item 10 is an optical construction comprising: a first major surfacecomprising a first plurality of waveguide alignment features; a firstplurality of optical waveguides with angle cleaved end faces disposedadjacent the first major surface, the angle cleaved end faces beingstaggered relative to one another; a second major surface opposite thefirst major surface and comprising a second plurality of waveguidealignment features; and a second plurality of optical waveguides withangle cleaved end faces disposed adjacent the second major surface, theangle cleaved end faces being staggered relative to one another; whereineach optical waveguide in the first plurality of optical waveguidescorresponds to a different optical waveguide in the second plurality ofoptical waveguides, the angle cleaved faces of corresponding opticalwaveguides being so oriented that light exiting one optical waveguideenters the corresponding optical waveguide.

Item 11 is the optical construction of item 10, wherein the waveguidealignment features comprise parallel grooves.

Item 12 is the optical construction of item 10 or item 11, wherein theoptical waveguides comprise optical fibers.

Item 13 is the optical construction of item 10 to item 12, whereincorresponding optical waveguides are associated with one or morecorresponding microlenses for directing light between the angle cleavedend faces of the corresponding optical waveguides.

Item 14 is the optical construction of item 10 to item 13, wherein thestaggered angle cleaved end faces of each of the first and secondpluralities of optical waveguides form spaced apart first and secondrows of angle cleaved end faces.

Item 15 is the optical construction of item 10 to item 14, wherein eachof the angle cleaved end faces comprise a total internal reflection(TIR) surface.

Item 16 is the optical construction of item 10 to item 15, wherein eachof the angle cleaved end faces comprise a reflective material coating.

Item 17 is the optical construction of item 16, wherein the reflectivematerial coating comprises a metal or a metal alloy.

Item 18 is the optical construction of item 10 to item 17, wherein eachmicrolens includes a microlens diameter greater than a separationdistance between adjacent optical waveguides.

Item 19 is the optical construction of item 10 to item 18, furthercomprising an antireflective coating disposed on each microlens.

Item 20 is an optical construction, comprising: an opticallytransmissive substrate comprising: a first major side comprising a firstfloor surface; a first staircase formed on the first floor surface andcomprising at least a first step comprising a first tread; a secondmajor side opposite the first major side and comprising a second floorsurface; a second staircase formed on the second floor surface andcomprising at least a first step comprising a first tread; a firstplurality of staggered microlenses disposed on the second floor surfaceand forming rows of microlenses; a second plurality of staggeredmicrolenses disposed on the first tread of the second staircase andforming rows of microlenses, wherein the substrate, the first and secondstaircases and the microlenses form a unitary construction; a firstplurality of optical waveguides with angle cleaved end faces disposed onthe first floor surface, the angle cleaved end faces being staggeredrelative to one another; and a second plurality of optical waveguideswith angle cleaved end faces disposed on the first tread of the firststaircase, the angle cleaved end faces being staggered relative to oneanother, wherein each angle cleaved end face of an optical waveguide inthe first and the second plurality of optical waveguides corresponds toa different microlens so that light exiting each optical waveguide isdirected by the angle cleaved end face to the corresponding microlensthrough the substrate.

Item 21 is the optical construction of item 20, wherein the waveguidealignment features comprise parallel grooves.

Item 22 is the optical construction of item 20 or item 21, wherein theoptical waveguides comprise optical fibers.

Item 23 is the optical construction of item 20 to item 22, wherein aseparation distance between each angle cleaved end face of the opticalwaveguide and the corresponding microlens is a constant.

Item 24 is the optical construction of item 20 to item 23, wherein eachof the angle cleaved end faces comprise a total internal reflection(TIR) surface.

Item 25 is the optical construction of item 20 to item 24, wherein eachof the angle cleaved end faces comprise a reflective material coating.

Item 26 is the optical construction of item 25, wherein the reflectivematerial coating comprises a metal or a metal alloy.

Item 27 is the optical construction of item 20 to item 26, furthercomprising an antireflective coating disposed on the microlenses.

Item 28 is an optical connector comprising the optical construction ofitem 1 to item 27.

Item 29 is a transceiver comprising the optical construction of item 1to item 28.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe foregoing specification and attached claims are approximations thatcan vary depending upon the desired properties sought to be obtained bythose skilled in the art utilizing the teachings disclosed herein.

All references and publications cited herein are expressly incorporatedherein by reference in their entirety into this disclosure, except tothe extent they may directly contradict this disclosure. Althoughspecific embodiments have been illustrated and described herein, it willbe appreciated by those of ordinary skill in the art that a variety ofalternate and/or equivalent implementations can be substituted for thespecific embodiments shown and described without departing from thescope of the present disclosure. This application is intended to coverany adaptations or variations of the specific embodiments discussedherein. Therefore, it is intended that this disclosure be limited onlyby the claims and the equivalents thereof.

What is claimed is:
 1. An optical construction comprising: a pluralityof optical fibers with angle cleaved end faces; and an opticallytransmissive substrate comprising a first major surface, wherein theplurality of optical fibers is disposed in a same plane on the firstmajor surface such that the angle cleaved end faces are staggeredrelative to one another.
 2. The optical construction of claim 1, whereinthe first major surface comprises a plurality of waveguide alignmentfeatures, and each optical fiber in the plurality of optical fibers isreceived by a different waveguide alignment feature in the plurality ofwaveguide alignment features.
 3. The optical construction of claim 1,further comprising a plurality of microlenses on a second major surfaceof the optically transmissive substrate opposite the first majorsurface.
 4. The optical construction of claim 3, wherein the microlensesare staggered relative to one another.
 5. The optical construction ofclaim 3, wherein the angle cleaved end face of each optical fiber in theplurality of optical fibers corresponds to and is aligned with adifferent microlens.
 6. The optical construction of claim 5, wherein theangle cleaved end face of each optical fiber in the plurality of opticalfibers is oriented so that light exiting each optical fiber is directedby the angle cleaved end face to the corresponding microlens through thesubstrate.
 7. The optical construction of claim 5, wherein the anglecleaved end face of each optical fiber in the plurality of opticalfibers is oriented so that a central light ray traveling through theoptical fiber is reflected from the angle cleaved end face toward anoptical center of the corresponding microlens.
 8. The opticalconstruction of claim 3, wherein the second major surface defines arecessed area, the recessed area comprising the plurality ofmicrolenses.
 9. The optical construction of claim 8, wherein eachmicrolens in the plurality of microlenses has an apex disposed within avolume defined by the recessed area.
 10. The optical construction ofclaim 3, wherein the plurality of microlenses form spaced apart firstand second rows of microlenses and the angle cleaved end faces formspaced apart first and second rows of angle cleaved end faces.
 11. Theoptical construction of claim 3, wherein each microlens has a diametergreater than a separation distance between adjacent optical fibers. 12.The optical construction of claim 3, further comprising anantireflective coating disposed on each microlens.
 13. The opticalconstruction of claim 1, wherein a ribbon cable comprises the opticalfibers.
 14. The optical construction of claim 1, wherein each of theangle cleaved end faces comprise a total internal reflection (TIR)surface.
 15. The optical construction of claim 1, wherein each of theangle cleaved end faces comprise a reflective material coating.
 16. Theoptical construction of claim 1, wherein the first major surfacecomprises a first plurality of waveguide alignment features ending alonga first row and a second plurality of waveguide alignment featuresending along a different second row, the first and second rows beingparallel to each other, each optical fiber in the plurality of opticalfibers being received by a different waveguide alignment feature in thefirst or second plurality of waveguide alignment features.
 17. Theoptical construction of claim 1, wherein the angle cleaved end facescomprise a first plurality of end faces disposed along a first row and asecond plurality of end faces disposed along a second row, the first andsecond rows spaced apart from one another.
 18. The optical constructionof claim 17, wherein the first major surface comprises a raised portion,the first plurality of end faces disposed in recessed areas defined bythe raised portion.
 19. The optical construction of claim 18, whereinthe second major surface comprises a recessed area, the recessed areacomprising a plurality of microlenses, the angle cleaved end face ofeach optical fiber in the plurality of optical fibers corresponding toand being aligned with a different microlens in the plurality ofmicrolenses.
 20. The optical construction of claim 19, wherein a ribboncable comprises the plurality of optical fibers, the plurality ofoptical fibers having a fiber-to-fiber separation in the ribbon cable,each microlens being configured such that an optical bean diameter oflight exiting the microlens is greater than the fiber-to-fiberseparation.